X-ray apparatus



Jan. 10,1928.

F. 5. SMITH X-RAY APPARATUS Filed Dec. 8. 1926 INVENTOR.

A TT ORNE Y.

Patented J an. 1Q, 1928.

uau'rsn sra'ra 1,655,635 PATENT orrics.

FRANKLIN S. SMITH, OF BROOKLYN, NEW' YORK, ASSIG'NOR TO PRQBUCTS PROTEC- TION CORPORATION, A CORPORATION OF DELAWARE.

X-RAY errnna'rus.

Application filed December s, 1926. serial m. 153,281

lhis invention relates to X-ray apparatus r and systems and more particularly to k-ray apparatus adapted to operate at very high 1 I tne line 3'3 of Fig. 2.

potentials.

One of the objects of this invention is to provide an X-ray apparatus and, system which will be of simple and thoroughly practical construction and arrangement and capable of highly efficient action when in use. Another object is to provide apparatus of the above character in which a high voltage X- ray tube may be dependab ly and reliably operated while at the same time the achievement in a simple and thoroughly effective manner of the safeguarding of auxiliary apparatus against such high voltage is brought about. Another object is to provide an X- ray system and apparatus in which, while the initial source of potential is an alternating one, the X-ray tube may be operator with a uni-directional hi 'h potential and hence with a uni-directional current, but without endangering or over-stressing the rectifying device employed... Another object of this invention is to provlce a sys tem of the above-mentioned character in which a single rectifying thermionic valve may be safely employed in conjunction'with a plurality of appropriate condensers, but without subjectingsuch a valve to either the full potential applied to the X-ray tube itself or the total potential across'the condensers. Another object is to provide an apparatus and system of the above-mentioned type which will be well adapted to meet the varying conditions of hard practical use. Other objects will be in part obvious or in part. pointed out hereinafter.

i The invention accordingly consists in the features of construction, combinations of elements and arrangements of parts as will be exemplified in the structure to be hereinafter described and the scope of the application of which will be indicated in the following claims. 7

In the accompanying drawings in which are shown several of various possible embodiments of certain features of my invention, 1

Figure 1 is a diagrammatic representation of the circuits and apparatus of a preferred embodiment of my invention, certain mechanical features being shown in elevation; Figure 2 is a plan view as seen from the right of Fig. 1, showing the mechanical features of the high tension switch 2823- 29 of Fig. 1, and

Figure 3 IS a sectional view as seen along Similar reference characters refer to similar parts throughout the several views of the drawings. i

As conducive to a clearer understanding of certainfeatures of this invention, it may at this point he noted that in certain uses of the X-ray tube the characteristics of the lat ter when operated at very high potentials are desired to be made use of; while X- raytubes can be made to operate under and to withstand relatively high potentials, in

order to achieve in practice the advantages of such characteristics of the X-ray tube, yet the application of suchrelatively high potentlals to the tube gives rise tocertain serious difliculties and disadvantages in the apparatus associated with the X-ray tube and by or through which it is energized at this high potential. Such of these advantageous characteristics of the X-raytube as above outlined may be conveniently made" of practical use where the X-ray tube is connected so that itsinnnediate source of energy comprises two condensers connected in series, one of which is charged during the half cycle of an appropriate high tension alternating current and the next one is charged at the succeeding half cycle of'the same high potential current. An advantage ofsuch an arrangement resides in the fact that the condensers thus, in-series, provide an'appropriate high tension for energizing the X ray tube while, for charging the condensers, and individually, a potential substantially only half of that normally applied to the X-ray tube need be'employed. Such an arrangement is usually carried out in practice by the employment of uni-directional valves, conveniently of the hot cathode or thermionic type, for example; these valves insure the charging of the resoective condensers during the appropriate half cycles of the al-' ternating potential applied thereto and,

being unidirectional, also insure against the discharge of one condenser while the other is being charged.

But such a circuit arrangement, while achieving a number of desirable advantages has the very serious disadvantage that the rectifying or uni-directional valves become subjected to the full potential applied to the X-ray tube and either the potential applied to the X-ray tube must be therefore and necessarily limited to one which the rectifying valves themselves can withstand and thus the desired characteristics of the X-ray tube become unattainable, or the rectifying valves become over-stressed, rapidly and quickly brealr down, and thus destroyed. A dominant aim of this invention is to provide an X-ray system and apparatus in which fullest advantage of the characteristics of a very high potential X-ray tubemay be taken while at the same time eliminating in a thoroughly practical way such defects, limitations and disadvantages as have just been pointed out, and to carry out this aim by utilizing only a single rectifying valve.

Referring now to the drawing and more particularly to Figure 1, there is shown at 10 an X-ray tube having a cathode 11 conveniently of the filament type and an appropriate anode 12 for coaction therewith; the cathode 11 may be supplied with heating current through any appropriate source as, for example, by means of a suitable transformer indicated generally at 13. Two suitable condensers 14: and 15 are connected in series through a grounded conductor 16 and these condensers 14 and 15 are in turn connected by the conductors 17 and 18 to the cathode 11 and anode 12 respectively of the X-ray tube 10. If, therefore, each condenser is individually charged from an appropriate source, the potential applied to the X-ray tube 10 will be substantially the sum of the potentials across-the charged condensers.

The condensers 14 and 15 are arranged to be successively charged from preferably the same source of potential, and the latter takes the form of a stepup transformer having a primary winding 19 and a secondary winding 20, one terminal of which is connected to the conductor 16 which connects the condensers 14 and 15 in series; this terminal of the windng 20 may be grounded as at G. The transformer 1920 is'of such aratio of transformation that the potential across the secondary winding 20 is appropriatefor suitably. charging each of the condensers 14 and 15; the primarywinding 19 may be energized from any suitable source of alternating potential.

Associated with the above described apparatus is a synchronously driven switching mechanism generally indicated at 2 1, together with a uni-lateral valve or kenotron generally indicated at 22. This synchronously operated switching mechanism 21 preferably comprises two electrodes 23 and 24c connected to a synchronous motor 25 through the shafts 26 and 27 respectively, the latter being suitably insulated or preferably of an insulating material so as to isolate the synchronous motor from the conductive parts of the switching mechanism.

The electrode 23 is preferably of a gen erally cylindrical shape with curved or sphere-like ends, as is also the case with the electrode 24. Electrode 23 is provided with a conductive blade 23 conveniently formed integrally therewith, and of such a len th that it ust clears the fixed terminals or electrodes 28 and 29, spaced 180 from one another in the plane of rotation of the blade 23. The electrodes 28 and 29 are preferably spherical. The blade 23 is shaped so as to provide an arcuate end portion (see Fig. 2) of an extent in the direction of the plane of rotation thereof sutiicient to insure the closure of the associated high tension circuit for a suflicient length of time. Moreover, the coaeting electrodes 28 and 29,'being preferably spherical, together with the blade 23 provide circuit controlling menibcrs well adapted to insure a proper-duration of the arcing over of the high tension current and moreover in a manner relatively noiselessly. But in order further to diminish the noise of the apparatus, the conductive blade 23 is, in cross-section, and as will be more clearly seen from Figure 3, given a stream-line shape effective to reduce to a minin'iun'i the air disturbances due to the speed of rotation of theblade 23 and thus likewise to reduce the resultant noise.

The rotatable electrode 25% is provided with a like blade 24S adapted to coact with the -lined terminals or electrodes and 31 likewise spaced 180 in the plane of rotation ofthe blade 2 1 and adapted to coact therewith in a manner substantially similar to the coaction of the blade 23" with its associated electrodes 28 and 29. The rotatable blades 23 and 24, however, are spaced, with respect to their axis of rotation in the partieular arrangement illustratively shown in the drawing, 180 from one another.

Electrode 2st and hence blade 21, coin nected by conductor 3% to one electrode, namely, the plate of the rectifying valve 22 and the electrode 23 and hence the blade 25 is connected by conductor 32 to the other electrode, namely, the cathode oriilament of thekenotron 22. The rectifying valve 22 is preferably of the thermionic type and its cathode 85, taking the form of a filament, may be heated from any suitable source such as a transformer generally indicated at 36.

Elect-rode 29 is connected by conductor 37 to one terminal of condenser 1%; electrode 31 is connected by conductor 38 to one terminal of condenser 15. Electrode 28 is conneeted by conductor 39 to the free terminal of the secondary winding 20 of the stepup transforn'ier 1920 and to this same terminal of the winding 20 electrode 30 is connected by conductor 40.

In the operation of the apparatus and sys* tem. the blades 23 and 24 of the switching mechanism 21 are driven synchronously by the synchronous motor 25, the various parts being so related that, at the peak of the potential of each half cycle, the blades 23 and 2% will be in coacting position with one of the fixed electrodes and will hence be in circuit closing relation. With the apparatus in the position shown in Figure 1, the condenser 14: receives a charge at the peak of the potential of one half cycle of the energy output of the secondary winding 20 of the transformer 1920. Bearing in mind that the blades 23 and 24c are rotating, the arcu ate end portion of each blade (as is more clearly seen in Fig. 2 with respect to the blade 223*) permits this charging circuit to remain closed for a sufficient length of time to permit the condenser let to receive an adequate charge, and this occurs throughout an appropriate portion of the peak of the potential half wave active at the time. potential of the condenser i l is thus raised, on being charged, to one that is commensuratewith if not entirely equal to the potential across the secondary winding 20 of the transformer 19-20.

The charging circuit thus effective will be seen to be substantially as follows, and the electron flow of charging current therein will be in the direction in which the said charging circuit is traced :-from one terminal of the secondarywinding 20, conductor 16, condenser 14, conductor 37 switch electrode 29, rotatable switch members 2323*,

conductor 32, cathode 35 of the unilateral valve or kenotron 22, anode 33, conductor 34-, rotatable switch members EMF-2d, switch electrode 30, conductor 40, and thus back to' the other terminal of the secondary winding 20. The electron flow of charging current through the condenser 14 will be seen to be in the direction in which the charging circuit has just been traced, as will be clear from the direction of the electron flow from the cathode 35 to the anode 33 of the valve 22; accordingly, the electron flow of charging current into the condenser 14- will be seen to be in the direction from the right to the left as the circuit of Fig. 1 is viewed in the drawing.

By the time that the next half cycle arrives and achieves a value of potential approaching that of the peak of this succeeding half wave, the synchronous motor 25' will have rotated the switch member 28 and 24- throughout 180, the switch blades 23 and 24 being thereby removed from coacting relation with respect to electrodes 29 and 30 respectively and being positioned for coaction with the electrodes 28 and 31 respectively.

The charging circuit for the other c0ndenser 15 is-thus completed and the electron flow of charging current therein will be seen to be in the direction in which the charging circuit is traced as follows :-from The , place,

one terminal of the secondary winding 20, conductor 39 ,sw1tch electrode 28, switch members 23-23, conductor 82, cathode of the valve or kenotron 22, anode 33, conductor 34L, switch members 2i-2 l, switch electrode 81, conductor 38, condenser 15, conductor 16, and thus back to the otherterminal of the secondary winding 20. The electron flow of charging current in this charging circuit will thus be seen to be in the direction of the electron flow of current from the cathode 35 to the anode 33 of the valve or l-renotron 22, and accordingly the electron flow of charging current through the condenser 15 will be seen to be in the direction from the right to the left as the diagram of Fig. 1 is viewed in the drawing.

The cycles of operation above described are thereu on repeated, the kenotron 22 insuring the charging of each condenser in appropriate direction and preventing the discharge of a charged condenser through the transforn'ier winding when the potential of the latter, in its cycles, decreases or reverses.

It might further be pointed out that the condensers 14: and 15 are successively charged at substantial rapidity, each being charged during one-half cycle of the alternating potential effective in. the high tension winding-20 of the'transformer 1920; if it be assumed that the lowtension winding 19 of the transformer is supplied with energizing current from a commercial source of alternating potential, for example, one of sixty cycles, it will further be seen that the successive and alternate charges to the con densers follow each other with great rapidity. T ie effect of this action is to make effective across the serially connected condensers 14: and 15, and hence across the conductors 18 and 17, a unidirectional potential of substantial constancy and substantially free from material pulsations or variations. The constancy of this unidirectional potential is further contributed to by the effect of the condensers themselves in tending to smooth out pulsations or variations. The electrodes of the X-ray tube 10 will thus have impressed upon them a unidirectional and relatively constant potential equivalent substantially to twice the potential of the high-tension winding 20 of the transformer.

While the electron flow of charging current through the condensers 14: and 153 takes as hereinbefore described, in the clirection from the right to the left as the diagram is viewed in Fig. 1 of the drawing, the electron flow of discharge current of the condensers through the X-ray tube .10 takes place in the reverse direction and hence in a circuit that may be traced as follows, the electron flow taking place in the direction in which the circuit is traced :condenser Ill) 1 1:, conductor 16, condenser 15, conductor 17,

cathode 11 of the X-ray tube 10, anode 12 and, by way of conductor 18, back to the condenser 14-. The electron flow of the current which thus energizes the I i-ray tube 10 will be seen to take place in the direc tion of the electron flow from the cathode 11 to the anode 12 of the X-ray tube 10.

But as these cycles of operation are repeated, a further and highly important action, due to certain structural features of this invention, takes place. As has hereinbefore been pointed out, the electrodes of the synchronously operated switching mechanisin 21 are of predetermined shape; the fixed electrodes, for example, are substan tially spherical while the main body portion of the rotatable electrodes, for example, the member 3, is generally cylindrical with rounded end portions. These conductive parts are so spaced and the radii of their various curved surfaces so chosen, that each fixed electrode, together with its associated rotatable electrode are substantially coronaless in their action and moreover, have a capacitance, when related to each other as are the members 23 and 28, for example, of Figure 1, equivalent to or preferably less than the capacity of the lrenotron 22. The circuit of condenser 15, with the parts positioned as shown in Figure 1, will therefore be seen to have included in it capac ity equivalent to that of the lrenotron and also the capacitance between the members 23 and 28; but by reason of the relative magnitudes of these capacitances, there is avoided a voltage drop across the kenotron in this circuit which will be greater than half the voltage across these two capacitances in series. The kenotron 22 is thus safeguarded against an inverse distribution of condenser potentials of such a nature as will over-stress, and cause breakage of, the kenotron 22.

The rotatable switch member 23 with its associated switch blade 23 will therefore be seen to constitute with a coacting fixed electrode what is in effect a variable capacitance included in the condenser charging circuits. Aside, therefore, from effecting the proper sequence insertion of the kenotron 22 in the two charging circuits of the condensers 14.- and 15. the synchronous apiiaratus 21 will thus be seen to bring about this effect by synchronously and alternatel changing the capacitance included in each condenser charging circuit from one whose value is adequate to permit the flow of charging current in the one circuit to one which is adequate not only to prevent the flow of charging current in this same circuit when the succeeding half cycle is Gfl' GClIlVQ, but also to so change the characteristics of the same circuit that the kenotron is effectively safeguarded against over-voltages.

-By way of illustration merely, and as further conducive to a clearer understanding of certain features of this invention, it might be assumed, for example, that the limiting potential which the lzenotron 22 can withstand safely is 100 kv. Each condenser lei and 15 may thus be charged at substantially this potential so that the available potential for operating the X-ray tube 10 is approximately or substantially 200 l-zv. Assuming further that the condenser 15 has been charged during one half ycle and that the condenser 14 is being charged during the next half cycle, the. potential across the condenser 15 wil-lbe 100 lav. (active in one direction) and the potential across the secondary winding 20 will be 100 av. and, with respect to thecharged ser 15, active in the same direction as the potential across the latter. Across conductors 3 and 40, for example, therefore, there will be active a potential equivalent to the sum of these two potentials, namely, 200 lU'. but'this high potential, bearing in mind the assumption that the limiting voltage that the henoti'on 22 can safely withstand is 100 l(v'., cannot be made effective at or upon the lrenetroii 22 since there is interposed in any c cuit through which it attempts to be ell'ective not only the gap between the fixed il-ecti'ode 31 and the rotatable electrode 24 well as the gap between the fixed electrode 28 and the rotatable electrode38) but also the capacitances of the electrodes forming these gaps. ever, being proportioned as hereinabove noted (that is, with the parts in the position shown in Figure 1) furthermore prevent an inverse distribution of condenser potentials.

taking place in such a manner that the kenotron 22 becomes over-stressed. Assuming that the capacitance of the thus interposed gap or gaps in the circuit in which the cumulative potential of 200 lrv. is substantially equal to the capacitance of the kenotron 22, then the cumulative potential of 200 kv, is distributed in this circuit so that a voltage of 100 kv. exists across the kenotron and a voltage of 100 lrv. exists acro s the capacitance formed by the gap elect odes. The assumption by the capacitance oi the gap electrodes of a substantial portion of this cumulative potential thus prev its the kenotron 22 from being subjected to the full cumulative potential above assumed to be 200 lrv.

It will thus be seen that the limiting voltage which the lrenotron can safely with stand need no longer limit the potentials applied to the X-ray tube itself, and need not therefore limit the action and characteristics of the latter. liloreover, it will be seen that the many advantages of utilizing a single uni-lateral valve may be effectively achieved, and moreover, with apparatus not These capacitances, how-.

only of effective safeguarding action but also capable of rugged and inexpensive construction. It will therefore be seen that there has been provided in this invention a system and apparatus in which the several objects hereinbefore noted, as well as many thoroughly practical advantages are successfully achieved. 7

As many possible embodiments may be made of the above invention, and as many changes might be made in the embodiment above set forth, it is to be understood that all matter hereinbefore set forth or shown in the accompanying drawing is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. In apparatus of in combination, an X-ray the character described tube, a pair of condensers serially connected and adapted to be bridged across the terminals of said X-ray tubes, means for alternately charging said condensers, said means comprising a source of alternating relatively high potential and uni-directional valve means, and

synchronously operated mechanism for successively connecting serially said source of change the constants of high potential, one of said condensers, and said valve means and then said source of high potential, said valve means, and the other condenser.

2. In apparatus of the character de-' scribed, in combination, a pair of condensers and means for uni-laterally and successively charging said condensers, said means including a source of alternating relatively high potential, uni-lateral valve means, and synchronously driven means adapted to effeet a periodic connection serially of one.

condense-r, said source of high potential, and said valve means, and adapted to the circuit of the to prevent the full said source and of impressed other condenser, thereby cumulative potential of said other condenser from being upon saidvalve means.

3. In apparatus of the character described, in combination, a pair of condensers and means for uni-directionally and successively charging said condensers, said means including a source of alternating relatively high potential. uni-lateral valve means, and synchronously driven circuit controlling means adapted to efiect a penodic connection serially of one condenser,

said source of high potential, and said valve means, and to interpose in the circuit of the other condenser and said source of high potential a gap, said gap being proportioned to prevent said valve means from being subjected to the full cumulative potential of said source of high potential and of said other condenser.

4. In. apparatus of the character described,

combination, condenser arranged eluding means effective to rially with a source of alternating relatively high potential, a uni-lateral valve, and a gap formed of two spaced electrodes, and means synchronously effective for substantially closing said gap, said gap-electrodes being shaped and spaced to have acapacity equal to or less than the capacity of said valve.

5. In apparatus of the character described, in combination, an X-ray tube, means including a source of alternating relatively high potential'for supplying energy to vsaid X-ray tube, and a synchronously driven switch for periodically permitting the flow of high tension energy from said source, said switch having a fixed terminal and a coacting rotatable circuit controlling member, the

latter comprising a main body portion and a denser at alternations of one polarity of said source, said mechanism including means-effective at alternations of other polarity for interposing in the circuit of said valve a potential drop of such an order that the valve is safeguarded against the combined potentials of said charged condenser and of said last-mentioned alternations.

7. In apparatus of the character described, in combination, an X-ray tube, a condenser for supplying energy to said X-ray tube, a source of relatively high alternating potential for charging said condenser, auni-lateral valve in the charging circuit of said condenser, a synchronously operated switch for closing said charging circuit of said condenser at alternations of one polarity'of said source, said switch having a capacitance, when in circuit-opening position of such a value that the potential drop therein is sufficient to safeguard the valve against the combined potentials of. said-charged condenser and of said last-mentioned alternain combination, a pair of condensers and means for uni-laterally and successively charging said condensers, said means including a source of alternating relatively high potential, uni-lateral valve means, and synchronously driven mechanism adapted periodically to effect a connection serially of one condenser, said source of. high potential, and said val means, said nice ianisrii' iiipose between llO charging connection of said source, one of saidcon lensers, and said valve and at a halt Wave of opposite sign to reverse the relation oi said valve in its serial connection. i

10. In apparatus of the character described, in combination, an X-ray tube, a source of alternating potential of a magnitude substantially half of: that appropriate for operating said X-ray tube,meais,tor energizing said Xsray tube comprising two 1 condensers connected in series, a unilateral valve, and means synchronously operative for connecting in series said source of potential, one of said condensers, and said valve and then said source of potential, the other condenser, and said valve.

11. In apparatus of the character described, in combination, an X-ray tube,,a source of alternating potential of a magnie tude substantially half. of that appropriate for operat'ng said X-ray tube, mean for energizing said X-ray tube comprising two condensers connected in series, a unilateral valve, and synchronously operative means adapted at a half-Wave of one sign to close a series circuit comprising said source, one of said condensers, and said valve and to effeet a series circuit including said source, the other of said condensers, said valve and a capacitance of a value suilicieut to safeguard said valve in said last-named circuit against the cumulative potentials oi. said source and said last-mentioned condenser, and at a halt- Wave of opposite sign to close a series circuit including said source, the other of said condensers and said valve and to effect a series circuit; includingsaid sourcc,said first-mentioned condensetxsaid valve, and acapacitance of a value suil'cient to safeguard said valve in said last-mentioned circuit against the cumulative potentials of said source and said first-mentioned condenser 12. In apparatus of the character described, in combination, two condensers, a

source of alternating potential, a uni-lateral valve, means connecting said condensers and saidsource for charging the condensers from said source so that one condenser and said source form part of ,a series charging circuit and the other condenser and said source form part of a second series charging circuit, and synchronously operative means for inserting said valve first in one series circuit and then in the other. e

13. In apparatus of the character described, in combination, tivo condensers,a source of alternating potential, a uni-lateral valve, means connecting said condensers and said source so that one condenser and said source form part of a series circuit and the other condenser and said source form part of a second series circuit, means forming a capacitance, and synchronously operative means for first inserting said valve in'one seriescircuit and said capacitance meansin the. other and theninsertingsaid valve in the other series circuit and said capacitance means by said valve, when, etlectivc in one circuit, is safeguarded against the cumulative potentials off said source and of the condenser in the other circuit.

l t. In apparatus 01" the character described, in combination, a condenser, a source of alternating potential for chargin said condenser, a uni-lateral valve connected so that said condenser is charged from said source at halt Waves of the latter of one sign, and means etl'ective during half Waves of the other sign for preventing the impression across said valve of the full cumulative Gll CCt of the potential of the charging con denser and the potential of the half wave of said other-sign.

15. In. apparatus of the character described; in con'ibination, a condenser, a source of alternating potential for charging said condenser, a uni-lateral valve connected that said coiulenser is charged from said source at half \vaves ot the latter of one sign, and ll'lOflIlS effective at half Waves of the other sign for changing the constants oi the circuit of said valve and for thereby causing a potential drop in the said circuit of such an order that the valve is Fillitlglllll'dfil against the combined potentials of the charged condenser and of the suppressed half Wave oi said source.

In testimony \vhereot, I have signed my name to this specification this lth day of December, 1926.

FRANKLIN S. SMITH.

in said first-mentioned circuit, Where 

